1. Chapter-7 Basic Wireless Concepts and Configuration

2. Introduction

3. Wireless LANs When using a laptop in another location, it is inconvenient to rely on a wired connection. In this topic, you will learn about wireless LANs (WLANs) and how they benefit a business. You will also explore the security concerns associated with WLANs. Portable communications have become an expectation in many countries around the world. You can see portability and mobility in everything from cordless keyboards and headsets, to satellite phones and global positioning systems (GPS). The mix of wireless technologies in different types of networks allows workers to be mobile

4. Wireless Technologies

5. Wireless LAN

6. Comparing a WLAN to a LAN Interference - intrusion, nosiness Inconsequential - petty,minor

7. Wireless LAN Components

9. Wireless LAN Standards

11. Wi-Fi Certification Wi-Fi certification is provided by the Wi-Fi Alliance (http://www.wi-fi.org), a global, nonprofit, industry trade association devoted to promoting the growth and acceptance of WLANs. Standards ensure interoperability between devices made by different manufacturers. Internationally, the three key organizations influencing WLAN standards are:  ITU-R  IEEE  Wi-Fi Alliance

12. Wireless NICs The building block components of a WLAN are client stations that connect to access points that, in turn, connect to the network infrastructure. The device that makes a client station capable of sending and receiving RF signals is the wireless NIC. Like an Ethernet NIC, the wireless NIC, using the modulation technique it is configured to use, encodes a data stream onto an RF signal. Wireless NICs are most often associated with mobile devices, such as laptop computers.

13. Wireless NICs

14. Wireless Access Points An access point connects wireless clients (or stations) to the wired LAN. Client devices do not typically communicate directly with each other; they communicate with the AP. In essence, an access point converts the TCP/IP data packets from their 802.11 frame encapsulation format in the air to the 802.3 Ethernet frame format on the wired Ethernet network.

15. Wireless Access Points

17. Wireless Routers Wireless routers perform the role of access point, Ethernet switch, and router. For example, the Linksys WRT300N used is really three devices in one box.  First, there is the wireless access point, which performs the typical functions of an access point.  A built-in four-port, full-duplex, 10/100 switch provides connectivity to wired devices.  Finally, the router function provides a gateway for connecting to other network infrastructures. The WRT300N is most commonly used as a small business or residential wireless access device.

18. Wireless Routers

19. Configurable Parameters for Wireless Endpoints

23. Client and Access Point Association A key part of the 802.11 process is discovering a WLAN and subsequently connecting to it. The primary components of this process are as follows: Beacons - Frames used by the WLAN network to advertise its presence.

24. Client and Access Point Association Probes - Frames used by WLAN clients to find their networks.

25. Client and Access Point Association Authentication - A process which is an artifact from the original 802.11 standard, but still required by the standard.

26. Client and Access Point Association Association - The process for establishing the data link between an access point and a WLAN client.

27. Unauthorized Access Security should be a priority for anyone who uses or administers networks. The difficulties in keeping a wired network secure are amplified with a wireless network. A WLAN is open to anyone within range of an access point and the appropriate credentials to associate to it. There are three major categories of threat that lead to unauthorized access:  War drivers  Hackers (Crackers)  Employees

28. Man-in-the-Middle Attacks One of the more sophisticated attacks an unauthorized user can make is called a man-in-the-middle (MITM) attack. Attackers select a host as a target and position themselves logically between the target and the router or gateway of the target.

29. Denial of Service 802.11b and g WLANs use the unlicensed 2.4 GHz ISM band. This is the same band used by most wireless consumer products, including baby monitors, cordless phones, and microwave ovens. With these devices crowding the RF band, attackers can create noise on all the channels in the band with commonly available devices.

30. Denial of Service

31. Wireless Protocol Overview

32. Authenticating to the Wireless LAN

34. Encryption Two enterprise-level encryption mechanisms specified by 802.11i are certified as WPA and WPA2 by the Wi-Fi Alliance: Temporal Key Integrity Protocol (TKIP) and Advanced Encryption Standard (AES). TKIP is the encryption method certified as WPA. It makes use of the original encryption algorithm used by WEP. TKIP has two primary functions:  It encrypts the Layer 2 payload  It carries out a message integrity check (MIC) in the encrypted packet. This helps ensure against a message being tampered with

35. Encryption

36. Controlling Access to the Wireless LAN

37. Configuring the Wireless Access Point

38. Configuring Security There are seven wireless security modes supported by the WRT300N, listed here in the order you see them in the GUI, from weakest to strongest, except for the last option, which is disabled:  WEP  PSK-Personal, or WPA-Personal in v0.93.9 firmware or older  PSK2-Personal, or WPA2-Personal in v0.93.9 firmware or older  PSK-Enterprise, or WPA-Enterprise in v0.93.9 firmware or older  PSK2-Enterprise, or WPA2-Enterprise in v0.93.9 firmware or older  RADIUS  Disabled

39. Configuring Security

44. Scan for SSIDs Step 1: On the Microsoft Windows XP toolbar system tray, find the network connection icon that looks similar to the one shown in the figure. Double-click the icon to open the Network Connections dialog box. Step 2: Click the View Wireless Networks button in the dialog box.

45. Scan for SSIDs Step 3: Observe the wireless networks that your wireless NIC has been able to detect.

46. A Systematic Approach to WLAN Troubleshooting

48. Summary